When we divide pokemon sagas individually, some were good, some bad some great in terms of story, development, utilization of main characters, atmosphere or creativity.
Hiowever if we judge pokemon anime as one big unity, journey set in one timeline, space and conrinuity?
I would say pokemon anime started to lose its destination and path it used to follow once Misty was removed from main cast.
Misty removal didn't just make this show lose great deal of unforced comedy, tension, clash and emotional touch this character deivered. Through her hotheaded, sarcastic, passionarte, cawring and mother like personality keeping Ash,. Brock and others in check. Serving as moral com'pass in main cast. Knowing how to pull out anger and agitation from others leading to amusing conflicts, how to establish strong friendship with others helping them to find themselves in romance or encourage to keep trying and do their best like she did with Brock being complete and complex as character bringing lot of turbulent turmoils and colorful interactions within cast,
Accompanied with her unique pokemon, original goals of becoming water pokemon master showing whole world how beautiful and charming water pokemon are. Exuding with mystery and giving us insight in legends about ancient sea spirits and mystical water artifacts which allowed that water masters understand their hearts and use them to full potential.
Or very strong and multidimensional sense for action having lot of untapped potential to be done so much more with character.
No, Misty removal when looking at things long term wise and bigger picture caused pokemon anime to lose its own heart. Artistic value and integrity in treating pokemon series like other shonen long running series. Such as One Piece, Naruto, Fairy Tail, DRagon Ball, Sailor Moon, Inuyasha etc, etc.
Who have stable well established main cast, consistent story which slowly and delicately builds on itself adding more depth and excitement to adventure aspect and personality of main protagonists. Consistent continuity which maintains contact with past, give insight to younger generations what events preceeded to current stage of maturity and experience main characters went through and how this affected journey and future as whole.
Ever since Misty was replaced by end of Johto pokemon started to lose its spirit and originality it used to have initially. Being supposed to be show with big continuity set in same timeline and universe, consistsent group of characters and on going plot based journey where characters and main hero dont stagnate or suffer rests. But use past experiences and knowledge acquired before in new situations working toward reaching final destination and promoting thrill of exploring new worlds, new people, traditions, pokemon and mysteries in pokemon world. Like One Piece for example does with Luffy and its crew.
Ever since Misty left and cast changing started it discouraged people from growing attached to main characters wanting to continue enjoy in its flud lively, enjoyable personality, see him/her go in new adventures and advance toward achieving their dreams.
Because imagine you care and enjoy when writers flesh out story of character making you learn more about him, growing as person. You grew to like his personality, pokemon and background. Your eagerly awaiting to have him learn new things and advance his goals, establish friendship with Ash and others bonding with them. That character on large part defines pokemon anime for you making thrill of journey, dynamic and storyline more exciting, richer through his/her presence.
But when writers finally made you emotionally invest in chsaracter, feel you could relate to him, give you gist of what his dreams involve starting to develop and mature. Just when they caught your interest and made you feel content that his/her story started to move somewhere they drop that character unfinished with potential for further growth ending wasted?
That same character you enjoyed in becomes abandoned and reduced at best to opening sequences and flashbacks disappearing from face of earth after one or at best two short cameos after departure?
Knowing there would be no point to invest in any main character(beside Ash) since writers would just replace them with unfinished stories and potential to go on more complex, creative stage of character development. With their impact and importance being forgotten about fading away.
It resulted in Ash stagnating never growing on more notable level in coming closer toward his dream at least passing first step.
Due to writers being able to get away with it and in extreme cases cause even soft resets(like Unova series did),.
Due to not existing one compact main cast whose formed relationships, history, experience, maturity sand influence they left on each other would translate itself to new region Ash travel through. Attesting to previous struggles, success and achievements Ash and co fulfilled before being vector on which future is built. Thus providing familiar faces with who viewers could associate pokemon anime promoting strong following having significance behind it.
Caused story to have broken continuity with little to no ties to past, make all those strong bonds and moral values developed between Ash and friends mean nothing in end when not even simple phone call happens after they are replaced let alone meeting in person.
That every plots, subplots and development started in previous region became irrelevant for future because of previous characters and events which influenced Ash and pokemon universe never being brought up.
Along with any started growth in emotional sense, hard work we saw Ash friends doing in achieving their dreams(like May, Misty, Dawn, Brock, Iris etc), all those lessons, insecurities and rough times they went through never being showed on screen.
Having zero importance and ending as nothing more than joke, since build up of started work writers made about character has no chance to see light of day. Because new characters who will end up unexplored and open stories will continue to come, while pushing to side older ones who have appeal, charm and so many things left unanswered in story to bring new fresh twist to pokemon anime and go fiorward.
Some may say im giving too much merit to one fictional character in this anime. But its not just character, but rather complete change of formula and image pokemon anime used to have developed around itself losing its direction. And how Misty departture started negative trend of exaggerated cast replacing hurting pokemon series continuity and integroty as storyline as wholre,
Having subpar 20 minute marketing gimmick nowadays(it was always there to promote games but this didnt came to expression so much back than), rather than creative, overarching memorable story having defined direction to follow and take its protagonists toward with something coming out of it eventually.
The AG-series was waaaay better than the original series. It only suffered from being Total Reboot, and awful storytelling at Ash's last battle in the Hoenn League.
Compare this to the OS, which bleeds through its skin: each and every character is overrepetitive, including Brock and Misty. The story most of the time goes nowhere, filled with fillers, Ash is even unrecognisable wether he still even exist at all during Johto. There is a lot of nonsense happening, contradictions, and lack of originality copying other shows.
Depends for who.
Because i still think in terms of comedy, emotion, creativity of plots,groupo dynamic and sense of synergy prevailing in interaction between companions original series treated this things far more adequatelly.
Its also interesting you say main cast was "repetitive" when Misty was known for very wide stream of emotions as her personality unfold out gradually with time going through significant character devepment emotionally(regarding conflicts with family, feelings for Ash, born determination and passion to become recognizable water expert mastering their use with encounter with people like Sakura, Lorelei from E4, Marina, Trinity, Andreas etc, helping strengthening her belief and love for this specie or in developing better appreciation for her pokemon like Psyduck for example). Growing visibly attached to her friends starting to view them in light of her " family" being willing to do anything to protect them(including risking her life) and help out when in doubt being clearly upset more than any other girl afterwards in leaving them behind.
Or how much in reality Ash grew, became more resprectful and selfcritic by time Johto reached its dusk stage under influence of Brock and Misty,. Becoming stronger trainer and giving him required flare and decisiveness to defeat nhis long term rival Gary, accomplish better result at pokemon league and develop better understanding of his own pokemon(like Charizard for example knowing that hes doing right thing in leaving him at Charific valley despite being heartbroken).
Arguably even Brock grew becoming more empathic, prpotective and copnsiderate as person compared to rathger cold, stoic demeanour initially. Becoming more supportive and caring for Ash and Misty. Often talking with later one about romance, love issues, their families or iking to joke together on Ash behalf(not out of malice but endearment showing how much friendship and group chemistry grew). While delivering lot of moral support and motivation for Ash to develop better strategies and gave him backbone, reassurance how if something goes wrong he can count on him.